The present invention relates to a covering member to be used as a transparent protective member for protecting solar cells of a solar battery. More particularly, the present invention relates to a covering member for solar battery, which is made of transparent films having moistureproof property and sunproof property to improve the impact resistance and durability of the solar battery.
In recent years, solar cells which directly convert sunlight to electric energy have been drawing the attention of people in view of effective utilization of natural materials and prevention of environmental pollution, and thus been developed.
A typical solar battery comprises, as shown in FIG. 17, a glass substrate 1 as a front side transparent protective member at a light-receiving side, a back side protective member (backside covering member) 2, ethylene-vinyl acetate copolymer (EVA) films 3A, 3B as sealing films arranged between the glass substrate 1 and the back side protective member 2, and solar cells or silicon photovoltaic elements 4 sealed by the EVA films 3A, 3B.
To manufacture this solar battery, the glass substrate 1, the sealing EVA film 3A, silicone photovoltaic elements 4, the sealing EVA film 3B and the backside covering member 2 are successively overlaid in this order and integrated together by fusing and crosslinking the EVA.
By the way, excellent durability against ultraviolet radiation is a prime requirement in front side transparent protective members for solar batteries. In addition, excellent moistureproof property is also a primary requirement in order to prevent inside wirings or electrodes from corroding due to moisture or water permeation. Accordingly, the glass plates are conventionally used as front side transparent protective members.
Though a glass plate has excellent sunproof property and moistureproof property, it also has heavy weight and poor impact strength so that it is easily broken.
If using a transparent resin film, no problem should arise in the weight and impact strength, However, there is no conventional resin film excellent in both sunproof property and moistureproof property. That is, though a fluororesin film made of 2-ethylene-4-fluoroethylene-copolymer (ETFE) or the like is known as a transparent resin film having excellent sunproof property, it has moisture permeability so that it is not suitable as the front side transparent protective member for solar batteries.
It is an object of the present invention to provide a covering member for solar battery and a sealing film having a function as a covering member for solar battery each of which can be used as a transparent protective member for solar cells of a solar battery, wherein said covering member and said sealing film are made of transparent films having moistureproof property and sunproof property so as to be effective for lightening the solar battery and improving the impact resistance and durability of the solar battery. It is another object of the present invention to provide a light-weight, high impact resistant, high durable solar battery using the aforementioned covering member as front side and/or back side protective members.
A covering member for solar battery according to a first aspect of the present invention is a covering member to be used as a transparent protective member for protecting solar cells of a solar battery, comprising: a transparent high-moistureproof film and a transparent high-sunproof film having excellent durability against ultraviolet radiation, wherein the transparent high-moistureproof film and the transparent high-sunproof film are integrally laminated to each other.
Since the covering member for solar battery is made by integrally laminating the transparent high-moisture proof film and the transparent high-sunproof film, the covering member has enough moistureproof property and sunproof property required as a transparent protective member for solar battery.
A covering member for solar battery according to a second aspect of the present invention is a covering member to be used as a transparent protective member for protecting solar cells of a solar battery, comprising: a transparent high-sunproof film and a transparent high-moistureproof film, wherein the transparent high-sunproof film and the transparent high-moistureproof film are integrally laminated with adhesive containing ultraviolet absorbing agent.
According to this covering member for solar battery, the moistureproof property required as a transparent protective member for solar battery can be ensured by the transparent high-moistureproof film, and the sunproof property can be ensured by the transparent high-sunproof film and the ultraviolet absorbing agent in the adhesive.
A covering member for solar battery according to a third aspect of the present invention is a covering member to be used as a transparent protective member for protecting solar cells of a solar battery, comprising: a transparent high-sunproof film and a transparent high-moistureproof film, wherein the transparent high-sunproof film and the transparent high-moistureproof film are integrally laminated with EVA resin adhesive containing ultraviolet absorbing agent and cross-linking agent.
According to this covering member for solar battery, the moistureproof property required as a transparent protective member for solar battery can be ensured by the transparent high-moistureproof film, and the sunproof property can be ensured by the transparent high-sunproof film and the ultraviolet absorbing agent in the EVA resin adhesive. In addition, the EVA resin adhesive itself has high moistureproof property and is excellent in weatherability when containing cross-linking agent. Therefore, the EVA resin adhesive is effective for improving properties of the covering member. The cross-linking agent to be mixed in the EVA resin adhesive may be organic peroxide.
A covering member for solar battery according to a fourth aspect of the present invention is a covering member to be used as a transparent protective member for protecting solar cells of a solar battery, comprising a high-sunproof and high-moistureproof film made by coating inorganic oxide on a surface of a transparent base film containing ultraviolet absorbing agent.
According to this covering member for solar battery, the moistureproof property required as a transparent protective member for solar battery can be ensured by a coating layer made of inorganic oxide, and the sunproof property can be ensured by the ultraviolet absorbing agent contained in the transparent base film.
A sealing film having a function as a covering member of the present invention is a sealing film having a function as a transparent protective member for protecting solar cells of a solar battery, comprising: any one of the aforementioned covering members for solar battery of the invention and an EVA film, wherein the covering member and the EVA film are integrally laminated to each other.
A solar battery of the present invention is a solar battery comprising: a front side protective member; a back side protective member; and solar cells which are sealed between the front side protective member and the back side protective member, wherein at least one of the front side protective member and the back side protective member is any one of the aforementioned covering members of the present invention.